We propose to study the specific interactions of astral and non-kinetochore microtubules (Mts) in chromosome movements and spindle elongation in astral, anastral and monopolar spindles. We will investigate the anchorage of Mts and the spindle pole in these three spindle types in different stages of division. We will follow in vivo the behavior of individual chromosomal fibers under experimental conditions in wich chromosome movements are reversibly arrested. We will undertake very precise correlations between the LM and EM image in order to study problems concerning the credibility of the EM image. New approaches to such studies have emerged from analysis of our latest data concerning the lateral interactions of Mts in the spindle and the ability to experimentally change the degree of such interactions during mitosis in living cells. The work will be done on newt tissue cultures and Haemanthus endosperm, both of which are characterized by exceptional clarity of mitosis. We plan to utilize, among other research tools, extensively a recently-developed light microscope (single side band edge-enhancement microscope (SSEE)) combined with a laser and a UV microbeam microscope with strain free optics. We will perform extensive experiments utilizing a "minimal or simplified spindle", i.e. a spindle containing predominantly one type of Mts (kinetochore Mts). The work proposed is focused on defining the characteristic structure of such "barely functional spindles". We believe that the questions we are asking are important for a basic understanding of mitosis irrespective of how the results are interpreted; therefore, theoretical interpretations are not stressed in this application.